Near Field Performance of River Multi-port Diffuser

Abstract

This research program was carried out to develop a set of empirical formulae

•which can be used for the design of thermal power plant outfall structure discharges hot water into shallow or relatively deep river. These empirical formulae indicate the effect of the outfall structure and river parameters on the concentration of hot water into the river. The study included also a derivation of dimension-less curves for the range of river and outfall structure parameters typical of prototype river outfall installations. Another objective is to compare the formulae predictions with field measurements of a prototype river diffuser.

The use of these design formulae is very helpful in case of big thermal power plants. The amount of water required for cooling system in this plants is increased. The disposal of this water into rivers causes a high rise in its temperature and consequently a high thermal pollution is formed especially in case of low discharge and velocity of the stream. In this case, an outfall structure with high performance is required to achieve rapid dilution of the thermal waste water so that the temperature of the receiving water body does not exceed the maximum allowable temperature.

Submerged multi-port diffusers are generally considered to be most effective means of creating initial rapid dilution of thermal discharges. The diffuser discharges the flow through a large number of ports or nozzles, the total area available for entrainment is increased. This means that, provided adequate dilution water is available, excess temperatures can be reduced by a factors of 5 to 10 within a few meters of the ports.

In this study, a set of uni-directional multi-port diffusers were tested in a rectangular flume inside the northen experimental hall of the Hydraulics Research